Traffic signal control



Feb. 22, 1955 J. J, ALLES 2,702,896

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United States Patent O TRAFFIC SIGNAL CONTROL John J. Alles,Wilkes-Barre, Pa.

Application January 29, 1951, Serial No. 208,373

3 Claims. (Cl. 340-40) This invention relates to traffic signal controlsand particularly to an arrangement for varying the time cycle thereof inthe control of highway traic.

In highway traic signal arrangements, switching means normally will belocated at the various intersections for operating the trafiic signalsat said intersections, these controllers generally being termedsecondary control- 1ers. The secondary controllers have switch elementsAfor the purpose of sequentially lighting the usual green, amber and redlights at the intersections, or whatever combination of ligh-ts might beemployed.

lIn order to control sequentially the `ilow of traffic along a highway,-it is necessary to provide means Ito synchronize in a predeterminedrelationship, lthe various secondary controllers with a primary orcentral station. This is `accomplished Vnormally by means of pulses orcurrent interruptions at predetermined times for the purpose of bringingall of the secondary controllers into a predetermined relationship orsynchronism. `When it is desired to have a progressive flow of trafficalong a highway, it is necessary that arrangements be made so that -thechange in the main street green ligh-t, or 'a predetermined lightchange, occurs at progressive intervals along the highway, so that a carmoving along the street will be able to move at a predetermined speedwithout stopping, the green light occuring at the correct time. `In sucha control system, however, the cycle lshould be changed according to thedemand or time of day `and this has not been satisfactorily solved inprior devices.

iIn the prior art, the frequency applied to a synchronous motor has beenchanged to vary the speed. This is not satisfactory because it permi-tsonly a narrow range in `speed change because the torque of the motorfalls off with increase of speed and the torque requirements of atraflic signal controller remains constant.

`One of the objects of this invention is to provide a simplifiedarrangement for varying the cycle length of the secondary controllers ina highway traffic signal control system.

In a preferred aspect of the invention, the switching `elements of thesecondary -or local controllers can be operated by a synchronous orconstant speed motor arrangement. The arrangement can include a smallsynchronous or similar motor driving the switch operating mechanismthrough a casing having a gear train therein. As will be explained indetail hereafter, the gear train within the casing may have an armatureat the beginning of the gear train arranged so that the armature can berotated relative to the casing so as to provide a differential speedreduction. The gear train is connected to the switch operating mechanismand the friction therein is such that when the casing itself is turned,the switch mechanism will be turned, the gears and casing rotating as aunit. The armature can be energized, when desired, by a coil arrangementfed lfrom a central station energizing means. When it is desired tochange the cycle length, the armature can be driven in the direction ofthe rotation of the casing, only a small torque being required toovercome the friction in the gears. For example, the energy irnpressedcan be supplied by means of a square wave source -of current, such as acommutator means or by suitable electronic circuits. llt has been foundthat using standard sine wave alternating current for varying the speedof the cycle extension motor will permit a relatively small change inspeed to the cycle extension. lf a wave ydiffering from rthe sine wavefform, such as one more closely approaching a square wave as describedhereafter,

2,702,896 Patented Feb. 22, 1955 a much greater variation in speed canbe obtained and still maintain synchronism between the current supplysource and the cycle extension motor. The failure of Ithe cycleextension gearing, or any part of the speed varying mechanism, will notprevent driving of the control switch by the cycle extension drivingmechanism. Because of the fact that only the friction mustbe overcome,the power required for the speed variation purposes is a minimum whichmay become an important fact in a system having many controllers. Thefrequency can be controlled to produce the desired cycle length.

-In the drawings:

IFigure 1 illustra-tes a local or secondary station, schematicallyshowing a traiic signal and the means controlled by the drivingmechanism of the cycle extension mechanism of the present invention.

'Figure 2 is an enlarged view, partially in section, of the `drivingmechanism.

lFigure 3 is a view looking in the direction 3-3 of Figure 2.

lFigure 4 is a diagrammatic representation of a square wave.

Fig. 5 is an enlarged sectional View of the gear train and casing inFig. `2.

In Figure Il, one of the trac signal lights atan intersection isillustrated at 10 having -green light 11, amber light 12 and red light13. It is to be understood that the amber can be omitted or that othercombinations can be used. Cable 14 is illustrated connecting the lightswith the local or second-ary controller shown diagrammatically at l15.The secondary controller may take various forms, such as -for example,one similar to that illustrated in Patent No. 2,236,297, with theexception of the dial drive. 'In such a control arrangement, a dialhaving switch operating contacts usually is employed to sequentiallyoperate a solenoid rotating a cam shaft controlling Ithe circuits to thevarious lights. The solenoid has pulses fed thereto ywhen a change is to'be made which operates a ratchet means for rotating the cam sha-ft. Oneof the cams and one of the switches on the dial is used yfor the purposeof locally synchronizing the cam shaft with the dial once each cyclesuch, for example, as described in said patent. The localsynchronization can be accomplished in various manners and the secondarycontroller can take different forms. It is to be understood that variousmeans can b e used to rotate lthe dial as to operate the switchingcircuits.

The dial or switch operating mechanism of secondary controller I1'5 canbe driven by shaft 16 in any suitable manner. Shaft or loperator k16 canbe journalled in a plate '17, said shaft extending into gear casing -18and being connected with the train of gears 19 therein (Fig. 2). Thistrain may, for example, be composed of gear `30 on shaft i16, gear '30meshing with pinion 31, pinion 31 being carried on shaft `32 mounted onthe casing 18. Gear 33 can turn with shaft 32 and be meshed with pinion34, pinion 34 turning gear 35 which turns pinion 36. Gear 37 meshes withpinion 38 which is mounted on shaft 39. The friction between the gearsand the parts carried to -the'casing 1f8 is such that the shaft willturn with the casing 18 when the gear train is inactivated. The gearratio in said gear casing 18 is quite high, for example, 3600 to l.Casing -18 preferably has a reduced portion 20 connected with shaft 21.Shaft 21 is connected through gear train 19 in casing 18 with `asynchronous or constant speed motor 23. Synchronous motor 23 may be ofany suitable type.

When motor 23 is energized by la source of local power 25, shaft 21 andcasing 1-8 will be turned thereby. There is suicient friction in thegear train 19 so that shaft 16 will rotate with casing 18 so as todeliver the full torque of lthe motor 23. The inner end of the geartrain connected to shaft 24 preferably is located in the reduced portion20 of the -gear casing and has an armature 19' (Fig. 3) connectedtherewith.

Winding 26 is mounted on the laminated core structure 27. The core endsare suitably spaced and shaped so lthat the central aperture dened byits ends will surround or at least partially encircle the reducedportion `20 of the gear casing. The core and winding are arranged sothat they can influence or rotate the armature connected to the geartrain.

The winding 26 may be energized in various manners at `the desiredfrequency so as to produce the speed required of shaft 16 to drive thecontrol dial or switch means. If the winding is unenergized, the geartrain will turn with the casing because of friction therein, and shaft16 in turn will rotate at the same speed as the casing and shaft 21.

Winding 26 can be fed with alternating square wave pulses by variousmeans such being generated and controlled by a central station. Onemanner in which square waves can be supplied is illustratedschematically at 28 in Fig. 2. A source of direct current 29 feeds sliprings 30, said slip rings being suitably connected with commutatorsegments 31, 31. Shaft 32 is driven by motor 33 to rotate the commutatorsegments. Brushes or collectors 34 feed the alternating square wavepulses through leads 35 to winding 25. The speed of motor 33 can bevaried so as to control the `frequency and thus the speed of armature 19within casing 20. The square wave pulse means can be located in thecentral station and thus the cycle length of the secondary controllersadjusted accordingly at the central station.

Various types of square wave generating devices may be used such as, forexample, conventional electronic circuit arrangements. As anillustration only, the form of a square wave energy source isillustrated in Fig. 4. The shape of the square wave is such as to insurethe armature in the casing staying in step therewith. The core andwindings may be suitably arranged so as to be self-starting such as bythe shaded pole elements 35 (Fig. 3). Other similar alternating wave`forms -of course can be used. One of the purposes of modifying the sinewave form is to keep the armature in step over a greater range of speed.

The armature 19 and winding 26 are connected and arranged to rotate inthe direction which the casing tends to induce. Thus, the power requiredfrom winding 26 -is small because substantially all tha-t is necessaryis to overcome the friction involved.

It is evident that the details of construction can be varied withoutdeparting from the spirit of the invention except as defined in theappended claims.

What is claimed is:

1. In a traic signal control arrangement, the combination including asignal control switch having connections with the lights to becontrolled, a constant speed motor, a gear train connection and casingmeans holding said ygear train in which said gear train is rotatablymounted, said gear train having a driving shaft means, the frictionbetween the gears of said gear train rotatably locking said shaft meansand casing means to turn said shaft means with said casing means whenthe gear train is inactivated, said. gear train connection and drivingmeans being connected between said motor and signal control switch, anarmature connected to said gear train at a point spaced from said shaftmeans and operable to drive said gear train and shaft meansindependently of said driving means, reversing current means adjacentsaid armature for driving said gear train at a preselected speed, localsynchronizing means connected to said signal control switch, and meansremotely controlling the frequency of the reversing current so as tocontrol the cycle length by varying the speed of said shaft meansrelative to said casing.

2. `In a signal control device having a signal control switch and aconstant speed driving motor, the combination including a rotatablecasing means, a gear train including a plurality of meshed gearsrotatably mounted within said casing means and connected to a concentricrotatable shaft means extending exteriorly of said casing meansrotatable relative to said casing means, the friction between the gearsof said gear train rotatably locking said shaft means and casing meansto turn said shaft means with said casing means when the gear train isinactivated, said constant speed motor being connected to one of saidmeans, a driving connection connected to the other of said means, anarmature connected to said gear train means at a point spaced from saidshaft means driving said shaft means through said gear train means, andan armature energizing means adjacent said armature for energizing thesame to rotate said shaft means relative to said casing means.

3. In a signal control device, having a signal control switch means, aconst-ant speed motor means, the combination including a connectionbetween said constant speed motor means and an operator for said controlswitch means, comprising a casing shell and a gear train rotatablymounted therein, said gear train having a plurality of meshed gears onsubstantially parallel shafts in said casing shell, at least some ofsaid shafts being offset relative to the axis of the casing shell, saidgear train being connected to a driving shaft connection rotatablerelative to said casing when the gear train is activated and extendingexteriorly of said shell on its axis, and connected to said operator,the friction between the gears of said gear train rotatably locking saiddriving shaft connection with said casing shell to turn said shaftconnection with said casing shell when said gear train is inactivated,an electric motivating means including an armature connected to saidgear train to rotate the driving shaft connection relative to saidcasing to reduce the speed at which a control switch means is driven bysaid shaft connection when said electric motivating means is driven, andmeans energizing said electric motivating means in a speed reducingdirection, so as to reduce the drive speed of said control switch.

References Cited in the le of this patent UNITED STATES PATENTS1,703,178 Sifton Feb. 26,1929 1,802,630 Cotal Apr. 28,1931 2,451,457Shepherd Oct. 12,1948 2.459.429 Jeffers Jan. 18.1949

